The Phoenix Epidemiology and Clinical Research Branch was designated as the WHO Collaborating Center for Design, Methodology and Analysis of Epidemiological and Clinical Investigations in Diabetes in 1986. The purposes of the Center are to collaborate with the World Health Organization in the implementation of the WHO/IDF action program to provide advice, consultation and collaboration with other investigators in the design, methodology and analysis of epidemiology and clinical diabetes (NIDDM) and its complications. The center assists in the development and application of standardized methods for epidemiological and clinical investigations and data analysis relating to the etiology and pathogenesis of non-insulin-dependent diabetes (NIDDM) and its complications. The Center collaborates with those interested in applying such techniques elsewhere. The Center will advise and help in the design of new studies, including on-site assistance when necessary. The Center serves to train investigators from many parts of the world in diabetes epidemiology and clinical research. The Center participates in the WHO Multicenter Study of Vascular Disease in Diabetes, which is examining the mortality and incidence of vascular complications of diabetes among different ethnic groups in different countries. During the present year the Center has been involved in a WHO sponsored Diabetes Epidemiology training course in Cameroon, Africa, a WHO Consulting Group on the Classification and Diagnosis of Diabetes Mellitus and Its Complications, planning epidemiological studies in Argentina and training investigators from Japan, Korea and the United Kingdom.